Add 301_Remove_Invalid_Parentheses.java

Author: Sean Prashad

Strings/301_Remove_Invalid_Parentheses.java

@@ -0,0 +1,60 @@
+class Solution {
+ public List<String> removeInvalidParentheses(String s) {
+ List<String> result = new ArrayList<>();
+
+ if (s == null) {
+ return result;
+ }
+
+ Queue<String> q = new LinkedList<>();
+ Set<String> visited = new HashSet<>();
+
+ q.offer(s);
+ visited.add(s);
+
+ boolean finished = false;
+
+ while (!q.isEmpty()) {
+ s = q.poll();
+
+ if (isValid(s)) {
+ result.add(s);
+ finished = true;
+ }
+
+ if (finished) {
+ continue;
+ }
+
+ for (int i = 0; i < s.length(); i++) {
+ if (s.charAt(i) != '(' && s.charAt(i) != ')') {
+ continue;
+ }
+
+ String t = s.substring(0, i) + s.substring(i + 1);
+
+ if (!visited.contains(t)) {
+ q.offer(t);
+ visited.add(t);
+ }
+ }
+ }
+
+ return result;
+ }
+
+ private boolean isValid(String s) {
+ int count = 0;
+
+ for (int i = 0; i < s.length(); i++) {
+ if (s.charAt(i) == '(') {
+ count++;
+ }
+ if (s.charAt(i) == ')' && count-- == 0) {
+ return false;
+ }
+ }
+
+ return count == 0;
+ }
+}